photo: caroline o marcel/pexels
Industrial-scale deep-sea mining activities tested on the floor of the eastern Pacific Ocean have been shown to significantly reduce the abundance and diversity of marine life living in deep-sea sediments, according to a new scientific study. Researchers say the early findings serve as a warning about the potential for widespread damage to ecosystems that exist thousands of meters below the ocean’s surface and remain among the least understood on Earth.
The study documents clear changes in the structure of macrofaunal communities — small animals that inhabit seafloor sediments — following a mining trial conducted in 2022. Within weeks of the test, researchers observed sharp declines in both the number of organisms and the variety of species present. Scientists say the results reinforce long-standing concerns that deep-sea mining could cause long-lasting, if not irreversible, harm to fragile ecosystems increasingly targeted for their mineral wealth.
Rapid Biodiversity Loss Along Mining Tracks
The research, titled “Impacts of an industrial deep-sea mining trial on macrofaunal biodiversity,” was published in the journal Nature Ecology & Evolution in December 2025. It found that the total density of macrofaunal organisms within the direct path of the mining vehicle declined by approximately 37 percent, while species richness dropped by about 32 percent just two months after the trial.
“These declines were both rapid and pronounced, even after accounting for the natural variability that characterizes deep-sea ecosystems,” Eva C.D. Stewart, one of the study’s lead authors explain in the journal. “What we are seeing is not just background fluctuation. It is a clear signal that deep-sea communities are highly vulnerable to large-scale physical disturbance.”
To reach these conclusions, the research team employed a Before–After–Control–Impact (BACI) study design, collecting data over two years prior to the mining test and comparing it with samples taken two months afterward. This approach allowed the scientists to distinguish between natural changes in the ecosystem and those directly attributable to mining activity.
The researchers also examined areas adjacent to the mining tracks that were affected by sediment plumes — clouds of fine particles stirred up and dispersed by the mining machinery. While these plume-impacted areas did not experience the same dramatic decline in total organism numbers as the directly mined zones, the composition of species shifted noticeably.
In these areas, a small number of species became more dominant while others declined, resulting in reduced overall diversity. According to the researchers, such changes suggest that the ecosystem had not returned to its original state, even if total organism counts appeared relatively stable.
“What’s important here is that ecosystem health is not just about how many organisms are present,” Stewart said. “It’s also about how those organisms interact and how diverse the community is. Changes in dominance patterns can have cascading effects throughout the food web.”
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A Hidden World of Extraordinary Diversity
The mining trial took place in a region of the Pacific known as the Clarion–Clipperton Zone, a vast abyssal plain that spans millions of square kilometers. The area is widely regarded by scientists as one of the most biologically diverse regions of the deep sea, despite its extreme depth of more than 4,000 meters.
Remarkably, the majority of species collected during the study have yet to be formally described by science. Researchers estimate that close to 90 percent of the organisms sampled belong to species that remain unnamed, highlighting how little is known about the ecosystems now being considered for industrial exploitation.
Scientists caution that deep-sea ecosystems typically recover extremely slowly from disturbance, if they recover at all. Evidence from earlier, smaller-scale experiments suggests that physical impacts on the seafloor can remain visible for decades, raising concerns that commercial-scale mining could lock in ecological damage long before its full consequences are understood.
Stewart and her colleagues emphasize that the short time frame of the study captures only the earliest stages of impact. Long-term effects, they say, could be far more severe as changes in species composition ripple through the ecosystem over years or even centuries.
Economic Pressure and Regulatory Debate
Interest in deep-sea mining has surged in recent years due to growing global demand for metals such as nickel, cobalt and copper, which are found in polymetallic nodules scattered across the seafloor. These materials are considered critical for batteries, renewable energy systems and other technologies central to the global energy transition.
However, the new findings add scientific weight to calls for stricter oversight — or even a temporary moratorium — on deep-sea mining until its environmental consequences are better understood. Conservation groups and some governments argue that exploiting ecosystems that are still largely unexplored poses unacceptable risks.
Deep-sea habitats play key roles in global processes, including carbon storage and nutrient cycling, and provide habitat for organisms that form the foundation of oceanic food webs. Disrupting these systems, scientists warn, could have far-reaching consequences beyond the deep ocean itself.
Researchers say the implications of the study extend far beyond the single mining trial it examined. If commercial operations proceed as planned, tens of thousands of square kilometers of deep-sea habitat could be disturbed in regions like the Clarion–Clipperton Zone alone.
Much of this area has already been allocated for exploration and potential extraction, raising the likelihood that large sections of the deep ocean could be damaged before scientists have a chance to fully document what lives there or understand how these ecosystems function.
The study adds to a growing body of evidence that the deep sea is not a barren wasteland, as once believed, but a living, complex and highly sensitive environment. As pressure mounts to tap its mineral resources, researchers say policymakers face a critical choice: proceed cautiously with incomplete knowledge, or risk permanently altering one of Earth’s last great wildernesses. (Wage Erlangga)
